Method and apparatus for transmitting and receiving reference signal in wireless communication system

ABSTRACT

The present invention relates to a method and an apparatus for transmitting and receiving a reference signal in a wireless communication system. In the method, in order to dynamically switch an uplink (UL) Demodulation-Reference Signal (DM-RS) according to the communication environment, such as CoMP and MU-MIMO, a parameter set for generation of a reference signal sequence is configured to include a Virtual Cell Identifier (VCID) parameter configured by information of a total of 9 bits and a cyclic shift hopping initial value parameter c init   CSH , which is 9-bit information representing one integer value among 510 integer values. Therefore, it may be possible to achieve dynamic transmission or reception of a reference signal and channel estimation through the dynamic transmission or reception of the reference signal even when the communication environment dynamically changes as in a Cooperative Multiple Point transmission and reception (CoMP) scenario.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.17/099,726, filed on Nov. 16, 2020, which is a Continuation of U.S.patent application Ser. No. 16/272,473, filed on Feb. 11, 2019, nowissued as U.S. Pat. No. 10,841,142, which is a Continuation of U.S.patent application Ser. No. 15/729,604, filed on Oct. 10, 2017, nowissued as U.S. Pat. No. 10,237,104, which is a Continuation of U.S.patent application Ser. No. 14/703,360, filed on May 4, 2015, now issuedas U.S. Pat. No. 9,787,514, which is a Continuation of U.S. patentapplication Ser. No. 13/891,522, filed on May 10, 2013, now issued asU.S. Pat. No. 9,025,485, and claims priority form and the benefit ofKorean Patent Application No. 10-2012-0050406, filed on May 11, 2012,which is hereby incorporated by reference in its entirety for allpurposes as if fully set forth herein.

BACKGROUND Field

The present invention relates to wireless communication, and moreparticularly, to a method and an apparatus for transmitting andreceiving a reference signal in a wireless communication system. Also,the present invention relates to a method of configuring a parameter fora reference signal in a wireless communication system and a signalingmethod for the same.

Discussion of the Background

Currently, various communication systems use a variety of referencesignals in order to provide information about a communicationenvironment to a counterpart apparatus through an uplink or a downlink.

Further, in order to enhance the communication capacity and performanceof a wireless communication system, a multi-cell cooperation orcooperation among transmission/reception points has been introduced. Themulti-cell cooperation is also referred to as “Cooperative MultiplePoint transmission and reception (CoMP)”. Techniques for CoMP include abeam avoidance technique in which adjacent cells cooperate with eachother to relieve interference to a user in a cell boundary area, and ajoint transmission technique in which adjacent cells cooperate with eachother to transmit identical data.

In the next generation wireless communication systems, such as Instituteof Electrical and Electronics Engineers (IEEE) 802.16m or 3rd GenerationPartnership Project (3GPP) Long Term Evolution-Advanced (LTE-A), one ofimportant requirements is to improve the performance of users who arelocated in a cell boundary area and are thus subject to severeinterferences from an adjacent cell. In order to address this problem,CoMP may be taken into consideration. A variety of scenarios may beemployed for CoMP.

Further, with the discussion about the Multi-User Multi-InputMulti-Output (MU-MIMO) technology as well as CoMP taken intoconsideration according to the development of wireless mobilecommunication systems, it may be necessary to properly discriminate orunify reference signals in various communication environments.

Therefore, aspects of the present invention provide a method ofconfiguring a parameter set for a reference signal sequence and a methodof signaling information required for the same, in order to perform adynamic switching to cause uplink reference signals to be identical toeach other or different from each other according to User Equipments(UEs) or signal transmission/reception points, in transmitting orreceiving the uplink reference signals used for estimation of a channelstate from a certain User Equipment (UE) by a signaltransmission/reception point, such as a cell or an evolved Node B(eNodeB).

SUMMARY

Aspects of the present invention provide a method and an apparatus fortransmitting a reference signal, and a signal signaling method for thesame.

Aspects of the present invention provide a method and an apparatus forconfiguring a parameter set used for generation of a certain uplinkreference signal by a UE in a CoMP system, and a method and an apparatusfor transmitting a reference signal by using the same.

Aspects of the present invention provide a method of performing adynamic switching to enable a UE to selectively generate and transmit anuplink reference signal according to the communication environmentbetween two types of uplink reference signals in a CoMP system, andconfiguring a parameter set for the two types of uplink referencesignals.

Aspects of the present invention provide a method of configuring aparameter set for two types of uplink reference signals used when a UEdynamically switches a reference signal according to a communicationenvironment between the two types of uplink reference signals, whereineach parameter set includes a Virtual Cell Identifier (VCID) and acyclic shift hopping initial value parameter

_(init) ^(CSH).

Aspects of the present invention provide a method of configuring aparameter set for two types of uplink reference signals used when a UEdynamically switches a reference signal according to a communicationenvironment between the two types of uplink reference signals, whereineach parameter set includes a cyclic shift hopping initial valueparameter

_(init) ^(CSH), which is 9-bit information representing one of 510integer values.

Aspects of the present invention provide a method of configuring aparameter set for two types of uplink reference signals used when a UEdynamically switches a reference signal according to a communicationenvironment between the two types of uplink reference signals, whereineach parameter set includes a cyclic shift hopping initial valueparameter

_(init) ^(CSH), which is 9-bit information representing one of 510integer values, and a Virtual Cell Identifier (VCID) configured by 9-bitinformation in total.

In accordance with aspects of the present invention, there is provided amethod of transmitting a reference signal by a User Equipment (UE) in awireless communication system, the method including: receivinginformation of one or more combinations of two parameter sets for twotypes of reference signals from a transmission/reception point, whereineach of the two parameter sets includes a cyclic shift hopping initialvalue parameter

_(init) ^(CSH), which is 9-bit information representing one of 510integer values; dynamically receiving indication information thatindicates a parameter set to be used for generation of the referencesignal between the two parameter sets; and generating and transmittingthe reference signal based on the parameter set indicated by theindication information.

In accordance with aspects of the present invention, there is provided amethod of receiving a reference signal by a transmission/reception pointin a wireless communication system, the method including: configuringand transmitting information of one or more combinations of twoparameter sets for two types of reference signals to a User Equipment(UE) in order to dynamically select a sequence of the reference signal,wherein each of the two parameter sets includes a cyclic shift hoppinginitial value parameter

_(init) ^(CSH), which is 9-bit information representing one of 510integer values; generating and transmitting indication information thatindicates a parameter set to be used for generation of the referencesignal between the two parameter sets to the UE; receiving the referencesignal which has been generated and transmitted by the UE based on theparameter set indicated by the indication information; and measuring achannel state of the UE from the received reference signal.

In accordance with aspects of the present invention, there is providedan apparatus to transmit a reference signal in a wireless communicationsystem, the apparatus including: a parameter set information receiver toreceive information of one or more combinations of two parameter setsfor two types of reference signals from a transmission/reception point,wherein each of the two parameter sets includes a cyclic shift hoppinginitial value parameter

_(init) ^(CSH), which is 9-bit information representing one of 510integer values; an indication information receiver to receive indicationinformation that indicates a parameter set to be used for generation ofthe reference signal between the two parameter sets; and a referencesignal processor to generate and transmit the reference signal based onthe parameter set indicated by the indication information.

In accordance with aspects of the present invention, there is providedan apparatus to receive a reference signal in a wireless communicationsystem, the apparatus including: a parameter set information processorto generate and transmit information of one or more combinations of twoparameter sets for dynamic switching of the reference signal to a UserEquipment (UE), wherein each of the two parameter sets includes a cyclicshift hopping initial value parameter

_(init) ^(CSH), which is 9-bit information representing one of 510integer values; an indication information processor to generate andtransmit indication information that indicates a parameter set to beused for generation of the reference signal between the two parametersets to the UE; a reference signal receiver to receive the referencesignal which has been generated and transmitted by the UE based on theparameter set indicated by the indication information; and a channelstate measurer to measure a channel state of the UE from the receivedreference signal.

It is to be understood that both forgoing general descriptions and thefollowing detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theprinciples of the invention.

FIG. 1 illustrates a wireless communication system to which embodimentsof the present invention are applied.

FIG. 2 illustrates an example of a method for transmitting PUSCHs,DM-RSs, and SRSs in an uplink of a wireless communication systemaccording to an exemplary embodiment of the present invention.

FIG. 3 is an enlarged view of the DM-RS 202 for UE 1 illustrated in theunit of a subcarrier, which is illustrated in the unit of a resourceblock in FIG. 2 , according to an exemplary embodiment of the presentinvention.

FIG. 4 illustrates a structure of a parameter set configured accordingto an exemplary embodiment of the present invention.

FIG. 5 is a signal flow diagram of a method for transmitting andreceiving a reference signal according to an exemplary embodiment of thepresent invention.

FIG. 6 is a block diagram illustrating a reference signal transmissionapparatus according to an exemplary embodiment of the present invention.

FIG. 7 is a block diagram illustrating a reference signal receiving andchannel state measuring apparatus according to an exemplary embodimentof the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription and drawings, the same reference numerals are used todesignate the same or similar components, and so repetition of thedescription on the same or similar components will be omitted. In thefollowing description, a detailed description of known functions andconfigurations incorporated herein will be omitted when it may make thesubject matter of the present invention rather unclear.

Further, in the following description, elements of the present inventionmay be named by using terms, such as the first, the second, A, B, (a),and (b). However, such terms are used only to discriminate thoseelements from other elements and do not limit the essence, sequence, ororder of the elements. If it is read that one element is “connected”,“combined”, or “attached” to another element, it should be understoodthat not only may the element be directly connected, combined, orattached to said another element but a third element may also beconnected, combined, or attached between the element and said anotherelement.

FIG. 1 illustrates a wireless communication system to which embodimentsof the present invention are applied.

A wireless communication system is widely arranged in order to providevarious communication services, such as services of voice and packetdata.

Referring to FIG. 1 , the wireless communication system includes a UserEquipment (UE) 10 and a transmission/reception point 20, which performsuplink and downlink communication with the UE 10.

In the present specification, the UE 10 will be interpreted to have aninclusive concept referring to a user terminal in a wirelesscommunication, and to include not only a UE in Wideband Code DivisionMultiple Access (WCDMA), LTE, and High Speed Packet Access (HSPA), butalso a Mobile Station (MS), a User Terminal (UT), a Subscriber Station(SS), a wireless device, etc. in Global System for Mobile Communications(GSM) or user terminals in other mobile communication systems.

The transmission/reception point 20 or the cell generally refers to astation communicating with the UE 10 and may be referred to as anothername, such as a Base Station (BS), a Node B, an evolved Node B (eNodeB),a Base Transceiver System (BTS), an access point (AP), and a relay node.

In the present specification, the transmission/reception point 20 or thecell will be interpreted to have an inclusive concept referring to anarea covered by a Base Station Controller (BSC) in CDMA, a Node B ofWCDMA, etc., and to have an inclusive concept implying all types ofdevices capable of communicating with one terminal, such as a microcell, a pico-cell, a femto cell, a site, a sector of a macro cell, arelay node, a Radio Remote Head (RRH) connected to a base station, etc.

In the present specification, the UE 10 and the transmission/receptionpoint 20 have inclusive meanings indicating two maintransmitting/receiving agents used to implement the technology ortechnical concept described herein and are not limited by the particularterms or words used herein.

Although FIG. 1 illustrates one UE 10 and a plurality oftransmission/reception points 20, the present invention is not limitedto the illustrated configuration. The present invention may be appliedto either a configuration in which one transmission/reception point 20communicates with a plurality of UE 10, a configuration in which one UE10 communicates with a plurality of transmission/reception point 20 orother configurations.

There is no limit in the multiple access schemes applied to the wirelesscommunication system. Embodiments of the present invention can beapplied to various multiple access schemes, such as Code DivisionMultiple Access (CDMA), Time Division Multiple Access (TDMA), FrequencyDivision Multiple Access (FDMA), Orthogonal Frequency Division MultipleAccess (OFDMA), OFDM-FDMA, OFDM-TDMA, and OFDM-CDMA.

Further, according to aspects of the present invention, uplinktransmission and downlink transmission can be applied to a Time DivisionDuplex (TDD) scheme using different times for transmission, a FrequencyDivision Duplex (FDD) scheme using different frequencies fortransmission, and a Hybrid Duplexing scheme corresponding to acombination of the TDD scheme and the FDD scheme.

Specifically, exemplary embodiments of the present invention can beapplied to the fields of asynchronous wireless communication, which hasevolved to the LTE and LTE-A through GSM, WCDMA, and HSPA, and thefields of synchronous wireless communication, which has evolved to CDMA,CDMA-2000, and Ultra Mobile Broadband (UMB). Aspects of the presentinvention are not limited to a particular wireless communication fieldand will be interpreted to include all technical fields to which theidea of the present invention can be applied.

Referring to FIG. 1 , the UE 10 and the transmission/reception point 20can perform uplink and downlink wireless communication with each other.

The transmission/reception point 20 may perform downlink transmission tothe UE 10. The transmission/reception point 20 can transmits a PhysicalDownlink Shared Channel (PDSCH) as a downlink data channel for unicasttransmission. Further, the transmission/reception point 20 may transmitcontrol channels, which include a Physical Downlink Control Channel(hereinafter, referred to as “PDCCH”) as a downlink control channel usedin order to transmit Downlink Control Information (hereinafter, referredto as “DCI”) including scheduling approval information for transmissionthrough an uplink data channel (e.g. a Physical Uplink Shared Channel;“PUSCH”) and downlink control information, such as schedulinginformation necessary for reception of a PDSCH, a Physical ControlFormat Indicator Channel (PCFICH) for transmitting indicatorsidentifying areas of a PDSCH and a PDCCH, and a Physical HARQ IndicatorChannel (PHICH) for transmission of Hybrid Automatic Repeat request(HARQ) confirmation with respect to uplink transmission. In thefollowing description, signal transmission/reception through eachchannel may be expressed as transmission/reception of the channel.

The UE 10 may perform uplink transmission to the transmission/receptionpoint 20. Further, the UE 10 may transmit a Physical Uplink ControlChannel (PUCCH) as an uplink control channel used in order to transmitUplink Control Information (UCI), which includes a scheduling requestthat requires resource allocation for transmission of uplink data, achannel state report, and an HARQ ACK (acknowledgement)/NACK (negativeACK), which reports on whether a downlink transmission block has beensuccessfully received or not.

The transmission/reception point 20 may transmit, in the downlink, aCell-Specific Reference Signal (CRS), a Multicast/Broadcast over SingleFrequency Network Reference Signal (MBSFN-RS), a UE-Specific referencesignal, a Positioning Reference Signal (PRS), and a Channel StatusInformation Reference Signal (CSI-RS).

The UE 10 may transmit, in the uplink, a Demodulation Reference Signal(DM-RS) and a Sounding Reference Signal (SRS).

FIG. 2 illustrates an example of a method for transmitting PUSCHs,DM-RSs, and SRSs in an uplink of a wireless communication systemaccording to an exemplary embodiment of the present invention. In FIG. 2, the horizontal axis corresponds to a time axis indicating symbolswherein the entire axis corresponds to one subframe. The vertical axiscorresponds to a frequency axis indicating Resource Blocks (RBs). Asdefined in 3^(rd) Generation Partnership Project (3GPP) TechnicalSpecification (TS) 36.211 V10.4.0 (2011-12), “3^(rd) GenerationPartnership Project; Technical Specification Group Radio Access Network;Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channelsand Modulation (Release 10)” (hereinafter “TS36.211”) and as shown inFIG. 2 , one subframe may include a plurality of symbols, e.g., 14symbols, and one subframe may include two slots. Further, as defined inTS36.211 and as shown in FIGS. 2 and 3 , a Resource Block (RB) mayinclude 12 subcarriers in frequency domain and may correspond to thelength of one slot (7 symbols for normal cyclic prefix) in time domain.Throughout the specification, exemplary embodiments of the presentinvention will be described based on the definition of the RB. However,aspects of the present invention are not limited as such. For example,the size of one RB may be defined differently (e.g., one RB may includedifferent numbers of subcarriers in the frequency domain and may havedifferent length in time domain). In the present discussion, thedisclosure of TS36.211 is incorporated herein by reference in itsentirety.

Referring to FIG. 2 , each UE (UE1, UE2, and UE3) may transmit a PUSCH201, 203, and 205, respectively, to another UE (UE1, UE2, and UE3)through one or more resource block(s) indicated by DCI. DM-RSs 202, 204,and 206, which are reference signals used in order to respectivelydemodulate PUSCH 201, 203, and 205 and transmitted by a corresponding UE(UE1, UE2, or UE3), may be transmitted in one or more resource block(s)(such as the resource blocks in which the corresponding PUSCH, e.g., aPUSCH 201, 203, or 205, is transmitted). Further, as shown in FIG. 2 ,the DM-RSs 202, 204, and 206 may be transmitted in a determined locationin the frequency axis and the time domain location of the DM-RSs 202,204, and 206 may be in one symbol of each of the two slots within thesubframe in the time axis. The SRS 207 transmitted by the UEs may betransmitted through the last symbol of the subframe.

The DM-RS 202, 204, and/or 206 may be associated with a transmission ofa PUCCH or the DM-RS 202, 204, and 206 may be associated with atransmission of a PUSCH 201, 203, and 205, respectively, (FIG. 2 shows aDM-RS associated with a transmission of a PUSCH). The DM-RS 202, 204, or206 is transmitted mainly for channel estimation for demodulation. Inthis event, the DM-RS 202, 204, or 206 is transmitted in each slotwithin each subframe in which a PUCCH or a corresponding PUSCH, e.g., aPUSCH 201, 203, or 205, is transmitted. Further, information of atransmission bandwidth (BW) of the DM-RS 202, 204, or 206, which may berepresented resource block by resource block, is associated withtransmission of a PUCCH or transmission of a corresponding PUSCH, e.g.,a PUSCH 201, 203, or 205. For example, as shown in FIG. 2 , the DM-RSs202, 204, and 206 respectively associated with the PUSCH 201, 203, and205 are transmitted in the corresponding resource block(s) to which thePUSCH 201, 203, or 205 is allocated. Therefore, the resource blockallocation information of the DM-RS is based on the resource blockallocation information of the PUSCH. In this event, the resource blocksin which the PUSCH 201, 203, or 205 is allocated to the corresponding UEdepend on a field value for resource block allocation of DownlinkControl Information (DCI).

FIG. 3 is an enlarged view of the DM-RS 202 for UE1 illustrated in theunit of a subcarrier, which is illustrated in the unit of resource blockin FIG. 2 , according to an exemplary embodiment of the presentinvention. For example, the DM-RS 202 for UE1 in FIG. 2 is transmittedthrough four resource blocks, wherein the four resource blocks (eachblock includes 12 subcarriers) include a total of 48 subcarriers r(0) tor(47).

Meanwhile, a current DM-RS sequence is transmitted after being mapped toall subcarriers within a resource block used for transmission of theDM-RS. In this event, the DM-RS sequence is generated with a length(M_(sc) ^(RS)=the number of used RBs×the number of subcarriers within acorresponding RB) corresponding to the RB used for transmission of aDM-RS, which is obtained by Cyclic-Shifting (CS) of a base sequence r_(u, v)(n) based on Zadoff-Chu sequence as shown in Equation (1) below.The number of subcarriers within the corresponding RB is usually 12, butis not limited as such.

In this event, the base sequence may be generated differently accordingto each cell and according to each slot (that is, values of u and v ofthe base sequence may be different according to the cell identifier andthe slot number within the subframe). The Cyclic Shift (CS) value α_(λ)may be generated differently according to each UE and each layer.

r _(PUSCH) ^((λ))(m·M _(sc) ^(RS) +n)=w ^((λ))(m)r _(u,v) ^((α) ¹ ⁾(n)=e^(jα) ^(λ) ^(n) r _(u,v)(n),0≤n<M _(sc) ^(RS)

-   -   m=0, 1, n=0, . . . ,M_(sc) ^(RS)−1, M_(sc) ^(RS)=M_(sc) ^(PUSCH)

α₂=2πn _(cs,λ)/12,n _(cs,λ)=(n _(DMRS) ⁽¹⁾ +n _(DMRS,λ) ⁽²⁾ +n _(PN)(n_(s)))mod 12  Equation (1)

The ‘u’ value of the base sequence refers to a sequence-group number,which is defined by Equation (2) below.

As noted in Equation (2), the sequence-group number ‘u’ can be obtainedby adding a group hopping pattern f_(gs) (n_(s)) and a sequence-shiftpattern f_(ss) and then performing a modulo 30 operation on the sum. Asa result, the sequence-group number ‘u’ may have a total of 30 valuesfrom 0 to 29.

As noted in Equation (2), the group hopping pattern f_(gh) (n_(s)) has avalue of 0 when the group hopping has been disabled, and has a valuedetermined by the cell identifier N_(ID) ^(cell) and the slot number(n_(s)) when the group hopping has been enabled. Further, as noted inEquation (2), the sequence-shift pattern f_(ss) is defined differentlyin a DM-RS for a PUCCH and a DM-RS for a PUSCH. Specifically, thesequence-shift pattern f_(ss) has a value determined according to thecell identifier N_(ID) ^(cell) in the case of a DM-RS for a PUCCH andhas a value determined according to the cell identifier N_(ID) ^(cell)and a value Δ_(ss) signaled from a higher layer in the case of a DM-RSfor a PUSCH.

Equation $\begin{matrix}{{u = {\left( {{f_{gh}\left( n_{s} \right)} + f_{ss}} \right){mod}30}};} & {(2)}\end{matrix}$ ${f_{gh}\left( n_{s} \right)} = \left\{ \begin{matrix}0 & {{if}{group}{hopping}{is}{disabled}} \\{\left( {\sum_{i = 0}^{7}{{c\left( {{8n_{s}} + i} \right)} \cdot 2^{i}}} \right){mod}30} & {{if}{group}{hopping}{is}{enabled}}\end{matrix} \right.$ f_(ss)^(PUCCH) = N_(ID)^(cell)mod30f_(ss)^(PUSCH) = (f_(ss)^(PUCCH) + Δ_(ss))mod30(Δ_(ss) ∈ {0, 1, …, 29})

Here, the pseudo-random sequence c(i) is defined by a length-31 Goldsequence, and a pseudo-random sequence generator shall be initializedwith

$c_{init} = \left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor$

at the beginning of each radio frame.

Meanwhile, the ‘v’ value of the base sequence mentioned above refers toa base sequence number within the sequence-group, which is defined byEquation (3) below. As noted in Equation (3), the base sequence number‘v’ is determined by the cell identifier N_(ID) ^(cell), the slot numbern_(s), and the value f_(ss) ^(PUSCH) defined by Equation (2) when thegroup hopping has been disabled and the sequence hopping has beenenabled, otherwise the base sequence number ‘v’ is 0.

Equation $\begin{matrix}{v = \left\{ \begin{matrix}{c\left( n_{s} \right)} & {{if}{group}{hopping}{is}{disabled}{and}{sequence}{hopping}{is}{enabled}} \\0 & {otherwise}\end{matrix} \right.} & (3)\end{matrix}$

Here, the pseudo-random sequence c(i) is defined by a length-31 Goldsequence, and a pseudo-random sequence generator shall be initializedwith

$c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$

at the beginning of each radio frame. An example of the pseudo-randomsequence c(i) defined by the length-31 Gold sequence is illustrated inTS36.211. For example, the pseudo-random sequence c(i) of length M_(PN),where n=0, 1, . . . , M_(PN)−1, is defined by

c(n) = (x₁(n + N_(c)) + x₂(n + N_(c)))mod2x₁(n + 31) = (x₁(n + 3) + x₁(n))mod2x₂(n + 31) = (x₂(n + 3) + x₂(n + 2) + x₂(n + 1) + x₂(n))mod2

where N_(C)=1600 and the first m-sequence shall be initialized withx₁(0)=1, x₁(n)=0, n=1, 2, . . . , 30. The initialization of the secondm-sequence is denoted by c_(init)=Σ_(i=0) ³⁰x₂(i)·2^(i) with the valuedepending on the application of the sequence.

Meanwhile, n_(cs,λ) used for calculation of the cyclic shift (CS) valueis obtained by performing a modulo 12 operation on a total of threetypes of parameter values as noted in Equation (1). In this event,different from the other parameters, the parameter n_(DMRS,λ) ⁽²⁾ hasdifferent values according to the UEs when it is transmitted, and istransmitted through a 3-bit value included in the DCI. Meanwhile,n_(DMRS) ⁽¹⁾ is a cyclic shift offset parameter of 3 bits andtransmitted with cell-specific manner. Further, n_(PN)(ns) relating toCyclic Shift Hopping (CSH) is defined by Equation (4) below.

N _(PN)(n _(s))=Σ_(i=0) ⁷

(8N _(symb) ^(UL) ·n _(s) +i)·2^(i)  Equation (4)

Here, the pseudo-random sequence c(i) is defined by a length-31 Goldsequence, and a pseudo-random sequence generator shall be initializedwith

$c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$

at the beginning of each radio frame.

Further,

^((λ)) corresponding to an orthogonal cover code (OCC) used in thegeneration of a DM-RS sequence has a value, which is also indicated bythe 3-bit value dynamically transmitted through the DCI. Table 1 belowshows an example of the 3-bit values used in order to indicaten_(DMRS,λ) ⁽²⁾ and

^((λ)), and values of the indicated n_(DMRS,λ) ⁽²⁾ and

^((λ)).

TABLE 1 Cyclic Shift Field in n_(DMRS, λ) ⁽²⁾ [w^((λ))(0) w^((λ))(1)]uplink-related DCI format λ = 0 λ = 1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ =3 000 0 6 3 9 [1 1] [1 1] [1 −1] [1 −1] 001 6 0 9 3 [1 −1] [1 −1] [1 1][1 1] 010 3 9 6 0 [1 −1] [1 −1] [1 1] [1 1] 011 4 10 7 1 [1 1] [1 1] [11] [1 1] 100 2 8 5 11 [1 1] [1 1] [1 1] [1 1] 101 8 2 11 5 [1 −1] [1 −1][1 −1] [1 −1] 110 10 4 1 7 [1 −1] [1 −1] [1 −1] [1 −1] 111 9 3 0 6 [1 1][1 1] [1 −1] [1 −1]

In the meantime, CoMP has CoMP scenario 1/2/3 environments in whichtransmission/reception points have different cell identifiers (IDs) anda CoMP scenario 4 environment in which transmission/reception pointshave the same cell identifier (ID).

Also, according to whether a UE is located at a cell edge, according towhether to apply the CoMP scheme, and according to the CoMP scenario, itmay be required to guarantee inter-cell (or inter-point) orthogonalityat the time of transmitting a reference signal to a UE. Also, when theinter-cell (or inter-point) orthogonality is not inevitably required,there may be a case in which a pseudo randomization orquasi-orthogonality state for inter-cell (or inter-point) interferencerandomization is guaranteed.

According to an exemplary embodiment of the present invention, when a UEtransmits uplink DM-RSs, the DM-RSs should have the same base sequencein order to guarantee the inter-cell orthogonality, and thisorthogonality can be secured through different cyclic shifts (CSs), asshown in Table 1, an orthogonal cover code (OCC), etc. In an inter-pointpseudo randomization or inter-point quasi-orthogonality state, theDM-RSs should have different base sequences.

Therefore, according to the communication environments, a dynamicswitching is necessary between a mode for randomizing an inter-cellinterference and a mode for providing an inter-cell orthogonality asdescribed above, which will be described below in more detail.

That is, a dynamic switching may be necessary between two configurationsets or parameter sets, and an exemplary adaptation scenario is asfollows.

There are a first mode, which requires generation of the same DM-RS basesequence among UEs in order to guarantee an inter-cell orthogonality oran inter-point orthogonality, and a second mode, such as a mode in apseudo randomization or quasi-orthogonality state, in which differentDM-RS base sequences are generated among UEs. Both the first mode andthe second mode may be subdivided according to the CoMP scenario.

In the first mode requiring the generation of the same DM-RS basesequence, a common base sequence should be generated within a CoMP setin the case of CoMP scenario 1/2/3. However, since cell IDs arebasically different from each other in CoMP scenario 1/2/3, it isnecessary to separately signal a common parameter for generating acommon DM-RS sequence to the UE.

Meanwhile, in the case of CoMP scenario 4 having the same cell ID, thereis no problem in generating a DM-RS sequence based on a cell ortransmission/reception point to which the UE belongs in accordance withone of the current schemes, e.g., the existing scheme in 3GPP Release 10including TS36.211 (for example, 3GPP LTE Release 10 (LTE Rel-10); Seealso e.g., TS36.211). That is, since the cell ID is the same amongtransmission/reception points in CoMP scenario 4, it is possible togenerate the same base sequence even when the base sequence is generatedin the current cell-specific scheme.

The second mode in which different DM-RS base sequences are generatedamong UEs is opposite to the first mode. That is, in CoMP scenario 1/2/3having different cell IDs, there is no problem in generating a DM-RSsequence based on a cell or transmission/reception point to which the UEbelongs in accordance with the current scheme (for example, LTE Rel-10).However, in CoMP scenario 4 having the same cell ID, it is necessary tosignal separate parameters to the UE in order to generate specific basesequences different according to the UEs or transmission/receptionpoints.

In other words, in the case of both CoMP scenario 4 and the second moderequiring generation of different DM-RS base sequences, since the cellID is identical among transmission/reception points and generation of abase sequence according to the current-cell specific scheme thus makesit impossible to generate different base sequences, a separate signalingis necessary in order to generate a UE-specific (or point-specific) basesequence.

As described above, two parameter sets may be defined and used fordynamic switching between the first mode and the second mode accordingto the communication environments.

A method for defining two parameter sets (including parameter sets A andB) may be implemented as follows without limiting the present inventionthereto.

First, parameter set A or the first parameter set may be defined as aparameter set for generating a base sequence based on a cell ortransmission/reception point to which the UE belongs according to thecurrent scheme (for example, LTE Rel-10). Since the first parameter setas described above is allowed to use the current cell ID without change,it could be transmitted to the UE through Radio Resource Control (RRC)signaling, etc. Of course, since it corresponds to information alreadyknown to the UE, it may not be separately signaled.

Further, parameter set B or the second parameter set may be defined as aparameter set for generating a common base sequence in the case of CoMPscenario 1/2/3 or a parameter set for generating different UE-specific(or point-specific) base sequences in the case of CoMP scenario 4,differently from the parameter set for the current cell ID, etc. Sinceparameter set B does not correspond to information already known to theUE, the transmission/reception point should separately configure andsignal parameter set B to the UE through RRC signaling. etc.

The configuration of the two parameter sets is not limited to the methoddescribed above. For example, parameter set A may be defined as a set ofparameters for generating a common base sequence (that is, existingparameters, such as existing cell ID, in the case of CoMP scenario 4 andparameters separately configured in the case of CoMP scenario 1/2/3) andparameter set B may be defined as a set of parameters for generatingdifferent UE-specific (or point-specific) base sequences (parametersseparately configured in the case of CoMP scenario 4 and existingparameters, such as existing cell ID, in the case of CoMP scenario1/2/3). The existing parameters may include cell ID defined in TS36.211.

Further, in addition to the operation of configuring and transmittingone or more combinations of the two types of parameter sets defined asdescribed above, the transmission/reception point may configure andtransmit “indication information,” which indicates one parameter set tobe selected for use in generation of a DM-RS from the two types ofparameter sets by the UE.

This indication information implies the followings according to theconfiguration of a network to which the UE belongs, for example,according to whether the CoMP scenario is CoMP scenario 1/2/3 or CoMPscenario 4.

In the case of CoMP scenario 1/2/3, the indication information indicateswhether to use a common base sequence for the inter-cell orthogonalityor different UE-specific (or point-specific) base sequences generatedbased on a cell (transmission/reception point) including the UEaccording to the existing scheme (for example, LTE Rel-10), andindicates a corresponding parameter set between two types of parametersets.

In the case of CoMP scenario 4, the indication information indicateswhether to use a common base sequence generated based on a cell(transmission/reception point) including the UE in order to secure theinter-cell orthogonality using the existing scheme (for example, LTERel-10) or the different UE-specific (or point-specific) base sequences,and indicates a corresponding parameter set between two types ofparameter sets.

The indication information, which indicates one parameter set to beselected for use in generation of a DM-RS from the two types ofparameter sets (including parameter set A and parameter set B), may bedynamically transmitted to the UE. The indication information may beeither explicitly indicated through an additional 1 bit included in theDCI or implicitly indicated in connection with an indication field (forexample, the RB allocation field or the CS field in Table 1) in relationto an uplink DM-RS in the existing DCI, without limiting the presentinvention thereto.

Also, there may be various schemes for determining parameters aselements of the two types of parameter sets, without limiting thepresent invention to the two exemplary schemes described below asexamples thereof.

In the first exemplary scheme, each parameter set includes a VirtualCell Identifier (VCID) by a base sequence index and a parameter of aninitial value

_(init) ^(CSH) for cyclic shift hopping.

That is, in the first exemplary scheme, the parameter set is configuredby {VCID,

_(init) ^(CSH)}. Specifically, parameter sets A and B may be expressedas {VCID₀,

_(init, 0) ^(CSH)}, {VCID₁,

_(init, 1) ^(CSH)}, respectively. Parameter sets A and B areindependently configured and parameters in each parameter set are alsoindependently configured. Further, a part or all of the parameters maybe transmitted to the UE through higher layer signaling, such as RRC.

Further, as described above, the indication information, indicating oneparameter set to be selected for use in generation of a DM-RS from thetwo types of parameter sets (including parameter set A and parameter setB), may be dynamically transmitted to the UE.

In the second exemplary scheme for configuration of the parameter set,parameters configuring each parameter set include a cell ID and asequence initial value as in the first exemplary scheme. However,between the parameter sets, one parameter set (for example, parameterset A) includes the same cell ID N_(ID) ^(cell) and sequenceinitialization value

_(init) as those of the existing communication scheme, LTE Rel-10, andthe other parameter set (for example, parameter set B) includes aninitial value

_(init) ^(CSH) for cyclic shift hopping and a Virtual Cell Identifier(VCID) requiring a separate signaling, as parameters thereof. That is,in the second exemplary scheme, parameter sets A and B may be expressedas {N_(ID) ^(cell),

init} (which corresponds to LTE Rel-10) and {VCID,

_(init) ^(CSH)}, respectively.

The Virtual Cell Identifier (VCID) parameter included in the parameterset of the first exemplary scheme and the second exemplary schemecorresponds to a parameter, which is applied in place of the parameterN_(ID) ^(cell) in Equation (2) defining a method of generating ‘u’ value(sequence-group number) of the base sequence and Equation (3) defining amethod of generating ‘v’ value (base sequence number within asequence-group number) of the base sequence, and may be differentlyexpressed, for example, as n_(ID) ^(RS), although it is expressed as aVCID in this specification.

The VCID value may be separately configured for parameter set A(parameters of which are configured by values for generating a commonuplink DM-RS sequence within the CoMP set) and parameter set B(parameters of which are configured by values for generating differentUE-specific (or point-specific) uplink DM-RS sequences) in the firstexemplary scheme.

Further, in the second exemplary scheme, between the two parameter sets,one parameter set in the case of generating a base sequence based on atransmission/reception point to which the UE belongs, as in e.g., LTERel-10, may have a value of N_(ID) ^(cell), and the other parameter setmay have a common value within the CoMP set or different UE-specific (orpoint-specific) values.

That is, the VCID value may be the same value as the existing valuen_(ID) ^(cell) in the case of generating a base sequence based on thecell (transmission/reception point) to which the UE belongs as in thecurrent communication scheme (for example, LTE Rel-10) in the exemplarysecond scheme, or may be a common value within a CoMP set or differentUE-specific (or point-specific) values in the first exemplary scheme.

Meanwhile, the parameter

_(init) ^(CSH) included in the parameter set corresponds to a parameter,which is applied in place of the parameter

_(init) in Equation (4) defining a method of generating n_(PN)(ns)relating to Cyclic Shift Hopping (CSH). In the present embodiment, theparameter

_(init) ^(CSH) is used as the same expression as a “cyclic shift hoppinginitial value parameter”. The “cyclic shift hopping initial valueparameter” is not limited to the expression of

_(init) ^(CSH) and may be expressed differently, for example, as N_(ID)^(csh_DMRS)

The value of the parameter

_(init) ^(CSH) may be separately configured for parameter set A(parameters of which are configured by values for generating a commonuplink DM-RS sequence within the CoMP set) and parameter set B(parameters of which are configured by values for generating differentUE-specific (or point-specific) uplink DM-RS sequences) in the firstexemplary scheme.

Further, in the second exemplary scheme, between the two parameter sets,one parameter set in the case of generating a Cyclic Shift Hopping (CSH)based on a cell (transmission/reception point) to which the UE belongs,as in e.g., LTE Rel-10, may have a value of

_(init) (wherein the value

_(init) may be a value which is not signaled but is calculated usingN_(ID) ^(cell), etc. as in e.g., LTE Rel-10), and the other parameterset may have a common value within the CoMP set or different UE-specific(or point-specific) values.

The configurations of the two types of parameter sets in the firstexemplary scheme and the second exemplary scheme as described above areexemplary, and other parameters may be added to the configurationsaccording to the use thereof.

Meanwhile, based on the scheme of configuring a VCID, which is a virtualcell ID parameter, i.e. based on the range in which the VCID parameteris usable, in the first exemplary scheme and the second exemplary schemeas described above, there may be three schemes including the virtualcell ID parameter configuration schemes 1 to 3.

Virtual Cell ID (VCID) Parameter Configuration Scheme 1:

In VCID parameter configuration scheme 1, the range of a value, whichthe VCID may have, is determined to be the same as N_(ID) ^(cell) in theconventional LTE Rel-10. That is, in VCID parameter configuration scheme1, the VCID parameter has an integer value among values from 0 to 503and can be expressed by a total of 9 bits.

Virtual Cell ID (VCID) Parameter Configuration Scheme 2:

VCID parameter configuration scheme 2 is similar to VCID parameterconfiguration scheme 1. However, in VCID parameter configuration scheme2, since N_(ID) ^(cell) is expressed by 9 bits, the range of a value,which the VCID may have, include the other values within the 9 bits aswell as the integer values from 0 to 503. That is, in VCID parameterconfiguration scheme 2, the VCID parameter has an integer value amongvalues from 0 to 511. Further, in VCID parameter configuration scheme 2,the VCID parameter can be expressed by a total of 9 bits.

Virtual Cell ID (VCID) Parameter Configuration Scheme 3:

In VCID parameter configuration scheme 3, the range of a value, whichthe VCID may have, is determined to be 510 values corresponding to thenumber of theoretical kinds of group hopping patterns f_(gh) (n_(s)) andsequence-shift patterns f_(ss) defined by Equations (2) and (3),respectively.

Specifically, in VCID parameter configuration scheme 3, the number ofpossible cases of the group hopping patterns f_(gh)(n_(s)) used forgeneration of an uplink reference signal (UL DM-RS) sequence is a totalof 17 from 0 to 16 as noted from the mathematical expression └N_(ID)^(cell)/30┘ in Equations (2) and (3) because N_(ID) ^(cell) has aninteger value among values from 0 to 503. Further, the number ofpossible cases of the sequence-shift pattern f_(ss) used for generationof an uplink reference signal (UL DM-RS) sequence is 30 from 0 to 29 asnoted from the mathematical expression f_(ss)^(PUSCH)=(f_(ss)+Δ_(ss))mod 30 in Equations (2) and (3). As a result, byusing the number of possible cases of the group hopping patterns f_(gh)(n_(s)) and the number of possible cases of the sequence-shift patternf_(ss), 510 values (=17×30) are obtained as the range of the VCID value.

Therefore, in VCID parameter configuration scheme 3, the range of avalue, which the VCID parameter may have, includes integer values from 0to 509, wherein the VCID parameter can be expressed by a total of 9bits.

That is, in each of VCID parameter configuration schemes 1 to 3, theVCID parameter is expressed by a total of 9 bits and thetransmission/reception point generates parameter sets A and/or Bincluding the VCID parameter expressed by 9 bits and then transmits thegenerated VCID parameter to the UE through RRC signaling.

Meanwhile, the

_(init) ^(CSH) parameter, which corresponds to a cyclic shift hoppinginitial value parameter, is a parameter used in place of

_(init) in Equation (4). For n_(PN)(n_(s)) relating to the Cyclic ShiftHopping (CSH) in LTE Rel-10, the value

_(init) is defined as

${c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}},$

as noted in Equation (4). Here, └N_(ID) ^(cell)/30┘ is expressed by atotal of 17 values from 0 to 16 and f_(ss) ^(PUSCH) is expressed by atotal of 30 values from 0 to 29. Therefore,

_(init) has a value among 0˜29, 32˜61, 64˜93, . . . , and 512˜541 (thatis,

_(init) may have one of the remaining integer values except for theinteger values having a remainder of 30 or 31 among integer values from0 to 541 when the integer values from 0 to 541 are divided by 32).

Schemes of configuring the cyclic shift hopping initial value parameter

_(init) ^(CSH) may include four schemes including

_(init) ^(CSH) parameter configuration schemes 1 to 4, which aredescribed below.

For reference, the parameter

_(init) ^(CSH) is used in place of

_(init) in Equation (4). In other words, when

_(init) ^(CSH) parameter configuration schemes 1 to 4 according toexemplary embodiments of the present invention are applied,

${c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}},$

which is a mathematical expression defining

_(init) of Equation (4) (Equation (4) defined in LTE Rel-10) describedabove, is replaced by Equations (5) to (8), respectively.

_(init) ^(CSH) parameter configuration scheme 1:

In

_(init) ^(CSH) parameter configuration scheme 1, the

_(init) ^(CSH) parameter is configured to have all integer values withina range from the minimum value of

_(init) to the maximum value thereof in LTE Rel-10 as noted in Equation(5). Therefore, the

_(init) ^(CSH) parameter configuring parameter sets A and/or B has aninteger value among values from 0 to 541 and is expressed by a total of10 bits.

_(init)=

_(init) ^(CSH) where

_(init) ^(CSH)∈{0,1,2, . . . ,541}  Equation (5)

That is,

_(init) ^(CSH) in parameter configuration scheme 1, thetransmission/reception point configures a parameter set including the

_(init) ^(CSH) parameter (10-bit information) of integer values from 0to 541 and transmits the configured parameter set to the UE, and the UEgenerates and transmits a reference signal by using the

_(init) ^(CSH) parameter included in a parameter set determined bypredetermined indication information without change as a sequenceinitialization value

_(init).

_(init) ^(CSH) parameter configuration scheme 2:

In

_(init) ^(CSH) parameter configuration scheme 2, the

_(init) ^(CSH) parameter uses all values expressed by 10 bits as notedin Equation (6) below. That is, while only integer values from 0 to 541are used in

_(init) ^(CHS) parameter configuration scheme 1, all values from 0 to1023, which can be expressed by 10 bits, may be used in

_(init) ^(CSH) parameter configuration scheme 2.

As described above,

_(init) ^(CSH) parameter configuration scheme 2 is different from

_(init) ^(CSH) parameter configuration scheme 1 in that

_(init) ^(CSH) parameter may have the other bit values within the 10bits in consideration that a total of 10 bits are used in parameterconfiguration scheme 1 among a total of 31 bits of the initializationvalue based on the Gold sequence.

Therefore, in

_(init) ^(CSH) parameter configuration scheme 2, the

_(init) ^(CSH) parameter may have an integer value within a range ofvalues from 0 to 1023 and is expressed by a total of 10 bits.

_(init)=

_(init) ^(CSH) where

_(init) ^(CSH)∈(0,1,2, . . . 1023)  Equation (6)

That is, in

_(init) ^(CSH) parameter configuration scheme 2, thetransmission/reception point configures a parameter set including the

_(init) ^(CSH) parameter (10-bit information) of integer values from 0to 1023 and transmits the configured parameter set to the UE, and the UEgenerates and transmits a reference signal by using the

_(init) ^(CSH) parameter included in a parameter set determined bypredetermined indication information without change as a sequenceinitialization value

_(init).

_(init) ^(CSH) parameter configuration scheme 3:

_(init) ^(CSH) parameter configuration scheme 3 uses only practicalvalues capable of configuring the

_(init) value in the conventional communication scheme (LTE Rel-10) asthe

_(init) ^(CSH) parameter, as noted in Equation (7) below.

That is, among 542 integer values from 0 to 541 expressed by a total of10 bits, the

_(init) ^(CSH) parameter may have one of only a total of 510 integervalues, which are the remaining integer values except for the integervalues having a remainder of 30 or 31 among the integer values from 0 to541 when the integer values from 0 to 541 are divided by 32. In otherwords, the

_(init) ^(CSH) parameter may have a value among 0˜29, 32˜41, 64˜93, . .. , and 512˜541, and can be expressed by a total of 10 bits.

In

_(init) ^(CSH) parameter configuration scheme 3 as described above, acase where the

_(init) ^(CSH) parameter has an integer value having a remainder of 30or 31 among the integer values from 0 to 541 when the integer value isdivided by 32 may be considered as an erroneous case.

_(init)=

_(init) ^(CSH) where

_(init) ^(CSH)∈{0,1,2, . . . ,541} and

_(init) ^(CSH) mod 32≈{30,31}  Equation (7)

That is,

_(init) ^(CSH) in parameter configuration scheme 3, thetransmission/reception point configures a parameter set including the

_(init) ^(CSH) parameter (10-bit information), which has one of theremaining integer values except for the integer values having aremainder of 30 or 31 among integer values from 0 to 541 when theinteger values from 0 to 541 are divided by 32, and transmits theconfigured parameter set to the UE, and the UE generates and transmits areference signal by using the

_(init) ^(CSH) parameter included in a parameter set determined bypredetermined indication information without change as a sequenceinitialization value

_(init).

_(init) ^(CSH) parameter configuration scheme 4:

In

_(init) ^(CSH) parameter configuration schemes 1 to 3 as describedabove, one of 542 integer values (configuration scheme 1), 1024 integervalues (configuration scheme 2), or 510 integer values (configurationscheme 3), which are expressed by a total of 10 bits, is used as the

_(init) ^(CSH) parameter, and the signaled

_(init) ^(CSH) parameter is used without change as a sequenceinitialization value.

However, in

_(init) ^(CSH) parameter configuration scheme 4, a

_(init) ^(CSH) parameter, which is one of 510 integer values from 0 to509 expressed by a total of 9 bits, is included in a signaled parameterset, and the UE calculates and uses a sequence initialization value

_(init) relating to a cyclic shift hopping by using Equation (8) and the

_(init) ^(CSH) parameter.

As described above, in

_(init) ^(CSH) parameter configuration scheme 4, the signaled

_(init) ^(CSH) parameter may have a total of 510 integer values from 0to 509, which are substantial values capable of configuring the

_(init) value in LTE Rel-10, as noted in Equation (8) below. Therefore,the signaled

_(init) ^(CSH) parameter is expressed by a total of 9 bits.

Although the

_(init) ^(CSH) parameter has one of 510 integer values from 0 to 509expressed by the 9 bits signaled in order to calculate the sequenceinitialization value

_(init) relating to the cyclic shift hopping in the above description,aspects of the present invention are not limited to this description andare available for use of another term or expression.

That is,

_(init) ^(CSH) in parameter configuration scheme 4, when a valuesignaled from a higher layer, such as an RRC layer, in place of

_(init) in Equation (4) is the

_(init) ^(CSH) parameter (this value may be expressed by another term oranother expression), the

_(init) value is determined by Equation (8) below.

Further, the

_(init) value determined by Equation (8) based on the

_(init) ^(CSH) parameter may have one of a total of 510 integer values,which are the remaining integer values except for the integer valueshaving a remainder of 30 or 31 among the 542 integer values from 0 to541 when the integer values are divided by 32, as in the configurationscheme 3.

Therefore, in comparison with

_(init) ^(CSH) parameter configuration schemes 1 to 3,

_(init) ^(CSH) parameter configuration scheme 4 can reduce one signalingbit. Also, in

_(init) ^(CSH) parameter configuration schemes 1 to 3, the signaledvalue

_(init) ^(CSH) is used without change as the

_(init) value. However, in

_(init) ^(CSH) parameter configuration scheme 4, the

_(init) value is determined by Equation (8) based on the signaled value

_(init) ^(CSH).

_(init)=└

_(init) ^(CSH)/30┘·2⁵+(

_(init) ^(CSH) mod 30) where

_(init) ^(CSH)∈{0,1,2, . . . ,509}  Equation (8)

As described above, in an exemplary embodiment of the present invention,a transmission/reception point, which estimates a channel by receivingan uplink reference signal, such as a DM-RS, configures two types ofparameter sets according to the communication environment, such as aCoMP scenario, and then transmits the configured parameter sets to theUE. Further, the transmission/reception point dynamically transmitsindication information, which indicates a parameter set to be actuallyused for generation of a reference signal between the two types ofparameter sets, to the UE, wherein the two types of parameter setsinclude a Virtual Cell Identifier (VCID) parameter and a cyclic shifthopping initial value parameter

_(init) ^(CSH), which is configured by one integer value among valuesfrom 0 to 509 expressed by a total of 9 bits in the case of

_(init) ^(CSH) parameter configuration scheme 4 (of course, the cyclicshift hopping initial value parameter

_(init) ^(CSH) may be expressed by a total of 10 bits the case of

_(init) ^(CSH) parameter configuration schemes 1 to 3).

The UE calculates an actual cyclic shift hopping initial value

_(init) by Equation (8) using the cyclic shift hopping initial valueparameter

_(init) ^(CSH) included in the parameter set, generates a referencesignal based on the calculated value, and then transmits the generatedreference signal to the transmission/reception point.

In this event, the Virtual Cell Identifier (VCID) parameter may alsohave an integer value among values from 0 to 509 expressed by a total of9 bits in the case of VCID parameter configuration scheme 3 (of course,the Virtual Cell Identifier (VCID) parameter may have an integer valueamong values from 0 to 503 (configuration scheme 1) or among values from0 to 511 (configuration scheme 2) expressed by a total of 9 bits in thecase of VCID parameter configuration scheme 1 or 2).

FIG. 4 illustrates a structure of a parameter set configured accordingto an exemplary embodiment of the present invention.

The parameter set illustrated in FIG. 4 corresponds to an example of aparameter set configured according to VCID parameter configurationscheme 3 and cyclic shift hopping initial value parameter

_(init) ^(CSH) configuration scheme 4.

The parameter set 400 includes a VCID parameter field 410 and a cyclicshift hopping initial value parameter

_(init) ^(CSH) field 420. In each of the VCID parameter field 410 andthe cyclic shift hopping initial value parameter

_(init) ^(CSH) field 420, 9-bit information expressing one integer valueamong a total of 510 integer values is filled.

Here, each of the VCID parameter and the parameter

_(init) ^(CSH) has an integer value, which can be expressed by 9 bitswherein only 510 integer values among 512 integer values from 0 to 511expressed by 9 bits may be selectively used as the integer value. Forexample, the

_(init) ^(CSH) parameter may have an integer value among 510 integervalues from 0 to 509.

FIG. 5 is a signal flow diagram of a method for transmitting andreceiving a reference signal according to an exemplary embodiment of thepresent invention.

The signal flow diagram illustrated in FIG. 5 shows both a UE, whichgenerates and transmits a DM-RS to a transmission/reception point, andthe transmission/reception point, which receives the DM-RS and thenestimates a channel state of the UE from the received DM-RS.

First, a method of transmitting a reference signal by a UE may include:receiving information of at least one parameter set between twoparameter sets for two types of reference signals from atransmission/reception point (S510); dynamically receiving indicationinformation that indicates a parameter set to be used for generation ofa reference signal between the two parameter sets (S520); and generatingand transmitting a reference signal by the parameter set indicated bythe indication information (S530), wherein each of the parameter setsincludes a Virtual Cell Identifier (VCID) parameter and a cyclic shifthopping initial value parameter

_(init) ^(CSH), the cyclic shift hopping initial value parameter

_(init) ^(CSH) is configured by one integer value among values from 0 to509 expressed by a total of 9 bits, and the UE calculates an actualcyclic shift hopping initial value

_(init) by a predetermined equation using the received cyclic shifthopping initial value parameter

_(init) ^(CSH) and generates the reference signal based on thecalculated actual cyclic shift hopping initial value.

Hereinafter, each operation will be described in more detail.

In operation S510, the UE receives a first parameter set and/or a secondparameter set, each of which includes a Virtual Cell Identifier (VCID)parameter and a cyclic shift hopping initial value parameter

_(init) ^(CSH) having one integer value among values from 0 to 509expressed by a total of 9 bits. Further, in the case of VCID parameterconfiguration scheme 3, the Virtual Cell Identifier (VCID) parameterincluded in each parameter set may also have one integer value amongvalues from 0 to 509 expressed by a total of 9 bits (of course, in thecase of VCID parameter configuration scheme 1 or 2, the Virtual CellIdentifier (VCID) parameter may have an integer value among values from0 to 503 (configuration scheme 1) or among values from 0 to 511(configuration scheme 2) expressed by a total of 9 bits).

In this event, information of each parameter set may be transmittedthrough both the first parameter set and the second parameter set.However, parameters having the same values as those in the existingcommunication scheme (for example, LTE Rel-10) may not be transmitted.That is, one of the two parameter sets may not be signaled.

The signaling of the parameter set information in operation S510 may beperformed through higher layer signaling, but aspects of the presentinvention are not limited thereto.

In operation S520, the indication information indicates one parameterset, parameters of which are to be used for generation of a UL DM-RSsequence, between parameter sets A and B, and may be either explicitlyindicated through an additional 1 bit or implicitly indicated, whereinthe indication information may be either included in or derived from DCIof a PDCCH, but aspects of the present invention are not limitedthereto.

In operation S530, the UE calculates an actual cyclic shift hoppinginitial value

_(init) by Equation (9) below using the cyclic shift hopping initialvalue parameter

_(init) ^(CSH) (having one integer value among values from 0 to 509)included in the parameter set indicated by the indication information,and generates the reference signal based on the calculated actual cyclicshift hopping initial value.

_(init)=└

_(init) ^(CSH)/30┘·2⁵+(

_(init) ^(CSH) mod 30)  Equation (9)

In the process of generating the reference signal in operation S530,which will be described in more detail, the UE calculates asequence-group number value (u) and a base sequence number value (v)within the sequence-group number by Equations (2) and (3) by using theVirtual Cell Identifier (VCID) parameter included in the parameter setdetermined by the indiation information, calculates n_(PN)(n_(s)) byusing the actual cyclic shift hopping initial value

_(init) calculated by Equation (9) using the cyclic shift hoppinginitial value parameter

_(init) ^(CSH) included in the parameter set as described above, andgenerates a final reference signal (DM-RS) sequence according toEquation (1).

Then, the UE maps the generated final reference signal (DM-RS) sequenceto Resource Elements (REs) of the corresponding resource block(s),generates SC-FDMA signals including the uplink DM-RS, and then transmitsthe generated SC-FDMA signals to the transmission/reception point. Asillustrated in TS36.211, a Resource Element (RE) may be a base unit ofresources in frequency and time domains, and a resource block mayinclude a plurality of REs.

Further, according to aspects of the present invention, a method ofreceiving a reference signal by a transmission/reception point mayinclude: configuring two parameter sets for two types of referencesignals and transmitting information of at least one parameter setbetween the two parameter sets to the UE (S510); dynamicallytransmitting indication information that indicates a parameter set to beused for generation of a reference signal between the two parameter setsto the UE (S520); receiving the reference signal, which is generated andtransmitted by the UE based on the parameter set indicated by theindication information (S550); and measuring a channel state of the UEby using the received reference signal (S560), wherein each of theparameter sets includes a Virtual Cell Identifier (VCID) parameter and acyclic shift hopping initial value parameter

_(init) ^(CSH), and the cyclic shift hopping initial value parameter

_(init) ^(CSH) may be configured by one integer value among values from0 to 509 expressed by a total of 9 bits. Further, the Virtual CellIdentifier (VCID) parameter included in each parameter set may beconfigured by one integer value expressed by a total of 9 bits.

The transmissions of a parameter set and indication information by thetransmission/reception point in operations S510 and S520 may beperformed as described above with respect to the operations S510 andS520 of the UE, thus detailed description thereof is omitted.

In the process of receiving the reference signal and measuring a channelstate by using the received reference signal in operations S550 andS560, which will be described in more detail, the transmission/receptionpoint receives SC-FDMA signals including a DM-RS and performs resourceelements de-mapping, so as to extract an uplink DM-RS sequence.

Specifically, the transmission/reception point generates the DM-RSsequence based on the parameter set information and the indicationinformation transmitted to the UE in the operations S510 and S520 andcompares the generated DM-RS sequence with a DM-RS sequence extractedfrom the received signal to measure the channel state.

As described above, in an exemplary embodiment of the present invention,a transmission/reception point, which estimates a channel by receivingan uplink reference signal, such as a DM-RS, configures two types ofparameter sets according to the communication environment, such as aCoMP scenario, and then transmits the configured parameter sets to theUE, wherein each parameter set includes a Virtual Cell Identifier (VCID)parameter and a cyclic shift hopping initial value parameter

_(init) ^(CSH), which is configured by one integer value among valuesfrom 0 to 509 expressed by a total of 9 bits. Further, the UE calculatesan actual cyclic shift hopping initial value

_(init) by Equation (8) or (9) using the cyclic shift hopping initialvalue parameter

_(init) ^(CSH) included in the parameter set, generates a referencesignal based on the calculated value, and then transmits the generatedreference signal to the transmission/reception point.

In relation to the types of parameters included in each parameter setand their configuration (the range of the parameter values), aspects ofthe present invention are not limited to the configuration shown in FIG.5 and may include at least one of Virtual Cell Identifier (VCID)parameter configuration schemes 1 to 3,

_(init) ^(CSH) parameter configuration schemes 1 to 4, and a combinationthereof.

FIG. 6 is a block diagram illustrating a reference signal transmissionapparatus according to an exemplary embodiment of the present invention.

The reference signal transmission apparatus as described above may beimplemented in connection with a UE, may be embedded in the UE, or maybe some aspects of the UE. The reference signal transmission apparatusmay include software and/or hardware or may utilize software and/orhardware of the UE. In order to perform one or more operations describedherein, the reference signal transmission apparatus and/or the UE mayinclude one or more processors, one or more memories, one or moretransmitters/receivers, modems, controllers, antennas, Radio Frequencyinterfaces, Air interfaces, and the like.

A reference signal transmission apparatus 600 may include: a parameterset information receiver 610 to receive information of at least oneparameter set between two parameter sets for two types of referencesignals from a transmission/reception point; an indication informationreceiver 620 to dynamically receive indication information thatindicates a parameter set to be used for generation of a referencesignal between the two parameter sets; and a reference signal processor630 to generate and transmit a reference signal based on parameters ofthe parameter set determined by the indication information, wherein eachof the parameter sets includes a cyclic shift hopping initial valueparameter

_(init) ^(CSH) configured by one integer value among values from 0 to509 expressed by a total of 9 bits.

Each of the parameter sets received by the parameter set informationreceiver 610 may include a cyclic shift hopping initial value parameter

_(init) ^(CSH), which is configured by one integer value among valuesfrom 0 to 509 expressed by a total of 9 bits, and a Virtual CellIdentifier (VCID) parameter configured by information of a total of 9bits.

Further, the information of each parameter set received by the parameterset information receiver 610 may be information of both the firstparameter set and/or the second parameter set. However, parametershaving the same values as those in the existing communication scheme(for example, LTE Rel-10) may not be signaled, and the signaling of theparameter set information may be performed through higher layersignaling, such as signaling from an RRC.

The indication information received by the indication informationreceiver 620 may be either additional 1 bit information explicitlyincluded in DCI of a PDCCH or information implicitly derived from DCI ofa PDCCH.

Further, the reference signal processor 630 calculates an actual cyclicshift hopping initial value

_(init) by c_(init)=└c_(init) ^(CSH)/30┘·2⁵+(c_(init) ^(CSH) mod 30)based on the cyclic shift hopping initial value parameter

_(init) ^(CSH) included in the parameter set determined by theindication information, and generates the reference signal based on thecalculated actual cyclic shift hopping initial value, and transmits thegenerated reference signal.

Specifically, the reference signal processor 630 calculates asequence-group number value (u) and a base sequence number value (v)within the sequence-group number by Equations (2) and (3) by using theVirtual Cell Identifier (VCID) parameter included in the parameter setdetermined by the indiation information, calculates n_(PN)(n_(s)) byusing the actual cyclic shift hopping initial value

_(init) calculated from the cyclic shift hopping initial value parameter

_(init) ^(CSH) included in the determined parameter set, generates afinal reference signal (DM-RS) sequence according to Equation (1), mapsthe generated final reference signal (DM-RS) sequence to ResourceElements (REs) of the corresponding resource block(s), generates SC-FDMAsignals including the uplink DM-RS, and then transmits the generatedSC-FDMA signals to the transmission/reception point.

FIG. 7 is a block diagram illustrating a reference signal receiving andchannel state measuring apparatus according to an exemplary embodimentof the present invention.

The reference signal receiving and channel state measuring apparatus(hereinafter “reference signal receiving apparatus”) may be implementedby a receiving point of an uplink reference signal, such as base stationor eNodeB. However, aspects of the present invention are not limitedthereto. The reference signal receiving apparatus may include softwareand/or hardware or may utilize software and/or hardware of the basestation (or eNodeB). In order to perform one or more operationsdescribed herein, the reference signal receiving apparatus and/or thebase station may include one or more processors, one or more memories,one or more transmitters/receivers, modems, controllers, antennas, RadioFrequency interfaces, Air interfaces, and the like.

A reference signal receiving apparatus 700 may include: a parameter setinformation processor 710 to configure or determine two parameter setsfor switching of reference signals (DM-RSs) and to transmit informationof at least one parameter set between the two parameter sets to the UE;an indication information processor 720 to generate and transmitindication information that indicates a parameter set to be used forgeneration of a reference signal between the two parameter sets to theUE; a reference signal receiver 730 to receive a reference signal, whichis generated and transmitted by the UE based on the parameter setindicated by the indication information; and a channel state measurer740 to measure a channel state of the UE by using the received referencesignal, wherein each of the parameter sets includes a cyclic shifthopping initial value parameter

_(init) ^(CSH) configured by one integer value among values from 0 to509 expressed by a total of 9 bits.

Further, each of the parameter sets may further include a Virtual CellIdentifier (VCID) parameter configured by information a total of 9 bits.

Further, the information of each parameter set transmitted to the UE bythe parameter set information processor 710 may be information of boththe first parameter set and/or the second parameter set. However,parameters having the same values as those in the existing communicationscheme (for example, LTE Rel-10) may not be signaled, and the signalingof the parameter set information may be performed through higher layersignaling, such as signaling from an RRC.

The indication information transmitted to the UE by the indicationinformation processor 720 may be either additional 1 bit informationexplicitly included in DCI of a PDCCH or information implicitly derivedfrom DCI of a PDCCH.

Further, the reference signal received from the UE by the referencesignal receiver 730 may be a DM-RS, which is a reference signalgenerated based on an actual cyclic shift hopping initial value

_(init) calculated by

_(init)=└

_(init) ^(CSH)/30┘2⁵+(

_(init) ^(CSH) mod 30)

based on the cyclic shift hopping initial value parameter

_(init) ^(CSH) by the UE.

The channel state measurer 740 receives SC-FDMA signals including theDM-RS transmitted by the UE and performs resource elements de-mapping ofthe received signal to extract an uplink DM-RS sequence. Then, thechannel state measurer 740 generates an actual cyclic shift hoppinginitial value

_(init) from the cyclic shift hopping initial value parameter

_(init) ^(CSH) signaled to the UE and a reference DM-RS sequence fromthe Virtual Cell Identifier (VCID) parameter, and compares the extracteduplink DM-RS sequence with the reference DM-RS sequence, so as tomeasure the channel state.

By configuring a parameter set including a cyclic shift hopping initialvalue parameter

_(init) ^(CSH) and a Virtual Cell Identifier (VCID) parameter accordingto the configuration scheme as described above and transmitting andreceiving a reference signal (DM-RS) by using the configured parameterset, it may be possible to achieve uplink reference signal switchingwith an optimum quantity of information.

In more detail, by configuring a Virtual Cell Identifier (VCID)parameter and a parameter set including a cyclic shift hopping initialvalue parameter

_(init) ^(CSH) having an integer value among values from 0 to 509expressed by a total of 9 bits, dynamic transmission or reception of areference signal and channel estimation through the dynamic transmissionor reception of the reference signal may be performed even when thecommunication environment dynamically changes as in a CoMP scenario.

Even in the case where all elements configuring an embodiment of thepresent invention are combined into a single element or operate as asingle combined element in the above description, aspects of the presentinvention are not limited to such an embodiment. That is, within thespirit or scope of the present invention, at least one element or allelements may be selectively combined for operation.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method of transmitting a reference signal by auser equipment (UE) in a wireless communication system, the methodcomprising: receiving a cyclic shift hopping (CSH) initial valueparameter and a virtual cell identifier (ID) parameter respectivelyconfigured by one of integer values in a range of 0 to 509 through ahigher layer signaling, wherein the higher layer signaling isindependently configured for each of the CSH initial value parameter andthe virtual cell ID parameter; generating a reference signal sequencebased on the CSH initial value parameter and the virtual cell IDparameter; and transmitting the reference signal based on the referencesignal sequence, wherein the generating the reference signal sequencefurther comprises: determining an initial value of a pseudo randomsequence relating to a cyclic shift hopping based on the received CSHinitial value parameter; determining a cyclic shift value for thereference signal sequence based on the determined initial value of thepseudo random sequence relating to the cyclic shift hopping; andgenerating the reference signal sequence based on the determined cyclicshift value.
 2. The method of claim 1, wherein the initial valuec_(init) of the pseudo random sequence relating to the cyclic shifthopping is determined by using the received CSH initial value parameterc_(init) ^(CSH) by$c_{init} = {{\left\lfloor \frac{c_{init}^{CSH}}{30} \right\rfloor \cdot 2^{5}} + {\left( {c_{init}^{CSH}{mod}30} \right).}}$3. The method of claim 1, further comprising: determining a basesequence of the reference signal sequence based on the received virtualcell ID parameter, and wherein the reference signal sequence isgenerated based both on the determined cyclic shift value and thedetermined base sequence of the reference signal.
 4. The method of claim1, wherein the higher layer signaling is a radio resource control (RRC)signaling.
 5. A user equipment (UE) to transmit a reference signal in awireless communication system, the UE comprising: a processor configuredto: receive a cyclic shift hopping (CSH) initial value parameter and avirtual cell identifier (ID) parameter respectively configured by one ofinteger values in a range of 0 to 509 through a higher layer signaling,wherein the higher layer signaling is independently configured for eachof the CSH initial value parameter and the virtual cell ID parameter,generate a reference signal sequence based on the CSH initial valueparameter and the virtual cell ID parameter, and transmit the referencesignal based on the reference signal sequence, wherein, in generatingthe reference signal sequence, the processor is further configured to:determine an initial value of a pseudo random sequence relating to acyclic shift hopping based on the received CSH initial value parameter;determine a cyclic shift value for the reference signal sequence basedon the determined initial value of the pseudo random sequence relatingto the cyclic shift hopping; and generate the reference signal sequencebased on the determined cyclic shift value.
 6. The user equipment ofclaim 5, wherein the initial value c_(init) of the pseudo randomsequence relating to the cyclic shift hopping is determined by using thereceived CSH initial value parameter c_(init) ^(CSH) by$c_{init} = {{\left\lfloor \frac{c_{init}^{CSH}}{30} \right\rfloor \cdot 2^{5}} + {\left( {c_{init}^{CSH}{mod}30} \right).}}$7. The user equipment of claim 5, the processor is further configuredto: determine a base sequence of the reference signal sequence based onthe received virtual cell ID parameter, and wherein the reference signalsequence is generated based both on the determined cyclic shift valueand the determined base sequence of the reference signal.
 8. The userequipment of claim 5, wherein the higher layer signaling is a radioresource control (RRC) signaling.